Asos is to start charging UK shoppers who frequently return large amounts of goods a fee of £3.95 to send items back unless they keep up to £40 worth of their order.

The online fashion retailer, which until now has made free returns of unused items within 14 days an important part of its offer in Britain, has written to some shoppers saying it has updated its “fair use” policy for orders made from 8 October.

Frequent returners signed up to the group’s Premier subscription service will have to keep at least £15 of their original order to escape a fee, while non-subscription shoppers who regularly send back large amounts will have to keep at least £40 of their orders.

The company has not defined what it deems to be a frequent rate of returns but one industry definition suggests a customer who sends back more than nine in 10 of the items they order over an extended period.

“As part of a small group of customers with a frequently high returns rate, you’ll now only get free returns when you keep £15 or more from your order. If you keep less than £15 from your order, we’ll deduct £3.95 from your refund,” a message sent to shoppers signed up to Asos’s subscription service reads.

Last November, Asos highlighted the battle against high return rates as a big part of its effort to cut costs in the year ahead as it tries to lift profits.

The retailer, which this week sold a majority stake in its Topshop business in order to pay down debts as sales continue to slide, said last year that the behaviour of 6% of shoppers led to a £100m hit to profits because they frequently order discounted items, of which they sent back a high proportion.

Online retailers have begun charging for returns amid an increase in items being sent back and the costs associated in handling unwanted items – including the environmental cost of disposing of items that cannot be resold. Retailers are getting ready for peak returns season – typically around the Black Friday discount day in late November.

Up to half of the clothing bought on websites is returned, depending on the retailer, and in 2022 the number of items sent back rose by 26% on 2021, according to the returns specialist ReBound.

“The market is transitioning to a paid returns model,” said Al Gerrie of the returns logistics company ZigZag. He said his company had “received several inquiries from other fashion retailers hoping to implement more paid returns, so the industry is clearly watching what Asos does”.

H&M, Boohoo, New Look and Uniqlo now charge for online returns – unless they are brought back to a store in person. Several other big players are thought to be weighing up introducing delivery fees in one way or another this year.

Asos and Next are among retailers that have already tried sending out letters to problem returners, warning them their accounts are being monitored.

Last year, Asos customers found to have continued to abuse the system were told they may have their account deactivated – although this affected fewer than 0.5% of those shopping on the site.

Boohoo has also reportedly begun deactivating the accounts of its Premier subscription customers if it has deemed that they have “unusually high returns activity”.

Asos, which has used free returns as a marketing tool in the UK, has experimented with charges elsewhere, billing those in the US and some European countries, such as Poland, Belgium or Portugal, if they send an item back after 14 days. In some countries all returns are subject to a charge unless an item is faulty or incorrect, including Australia.

Asos said: “We’re making this change so that we can continue offering free returns to all our customers.” It said UK customers with “a frequently high return rate whose shopping habits make offering them unconditional free returns unsustainable” could send back items without a fee as long as they kept a certain portion of their order.